A CV axle has two CV joints (an inner joint and an outer joint).  These joints allow the axle to transfer the engine’s power to the drive wheels at a constant speed while accommodating for the different travel conditions, including the up and down motion of the suspension and cornering.  Without constant-velocity joints, the axles would bind or break whenever the vehicle hit a bump in the road or turned a corner.

CV joints are packed with grease for lubrication.  To keep the grease in the joint and moisture, dirt and roadway grime out, the joint is covered with a rubber boot called a CV boot.  CV boots are made of a durable rubber that can withstand extreme weather and travel conditions.  Good quality CV boots can easily last 100,000 miles or more.  But, because they are constantly exposed to the elements, a CV joint boot can be damaged at any time.  For this reason, it is a good idea to routinely inspect your CV boots for damage.   If your vehicle has more than 125,000 miles – it is a good idea to check the CV joints more often.

CV axles rarely fail – it’s the CV joint(s) that fail and they typically only fail because of a damaged or torn CV boot.  When a CV boot fails due to age and wear, or is damaged by roadway debris, the grease that keeps the joint lubricated quickly leaks out of the joint and dirt, roadway grime and moisture enters the joint. When this occurs, the CV joint will soon fail.

A bad or failing CV joint will oftentimes make a clicking, popping or grinding noise, especially when turning.  At low speed, a bad CV joint may make a steady knocking sound every couple of seconds or so.  A bad CV joint can also cause a vibration that is felt in the steering wheel and floorboard of the vehicle – this may happen only at certain speeds.

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